Traditionally, self adhesive materials consist of a substrate to be printed coated with an adhesive on one side and a release liner on the adhesive side, which is removed while applying the same or a pre-printed, pre cut label on a particular object. Self adhesive material is known as PSA material as the adhesive when exposed to open environment, after removal of the backing liner, shall be applied simply by using specified pressure onto the front of the printed substrate and the object to which it is expected to adhere.
All PSA (pressure sensitive adhesive) coated materials, also known as self adhesive materials must have a release liner or a release coating. Usually it is a type of Silicon coating that assists easy release. Release liners are silicon coated papers, films, foils or fabrics. Silicon coating is done by application of solvent based/water based silicones. These are thermally cured or cured by Electron Beam or by UV radiation. Usually Sulphide pulp/chemically beaten pulp is used for making the paper as this makes the surface coating of silicon more easy due to less penetration. Sometimes primer-coated papers are also used. Similarly films with or without primers, like polyester/polypropylene/PE (polyethylene)/HDPE (high density polyethylene) etc are also used for silicon coating. Most of these liners are not biodegradable and so are not environmental friendly. Silicones coated with aid of solvents are also adding to pollution.
UV and EB cured silicones gives out high concentration of ozone gas and adds to the pollution levels. Water based silicones are still not very popular due to their non stability. Some of these release liners are not recyclable due to their complex construction, where incineration is the only alternative, thereby creating polluting and toxic gases.
Also, at the time of fixing a self adhesive material on a surface of an object, the release liner is removed and the adhesive layer side of the self adhesive material is pressed on the surface of the object. But due to the nature of the PSA, the problem of crease formation and misalignment, while applying a self adhesive material to a surface is rampant. This ends up in a lot of wastage.
There are self winding tapes (like packaging tapes, BOPP tapes, Cellophane/PVC tapes etc) which don't necessarily use silicon liners or silicon coating on the other side, but these are primer coated on one side and usually use untreated films for aiding its easy release but they do not use a backing liner nor do they use a water soluble film to protect the adhesive or enable it's easy release.
The contemporary methods for producing traditional self adhesive material with release liner have not addressed the need of printers nor have they addressed the environmental concerns, nor have they addressed cost concerns.
Thus, there has been a long felt need by the industry especially involving PSA industry, PSA printers, converters, outdoor signage users, outdoor advertising fraternity and others who require their end products that is capable of being processed by diverse means. None of the methods used earlier or in current practice are capable of making printable PSA materials without using a release liner.
The present invention relates to self adhesive materials, having a protective layer of water soluble film incorporated with surfactants, which will totally eliminate the need for release liners. This will avoid the need of laminating the PSA coated face material with a release liner or to coat the face materials with silicon (like in case of some PSA tapes).
Also there will be no problem of crease formation as the printed face material/label could be adjusted/repositioned properly because of the inbuilt surfactants and fillers and will also help in faster breakage and dissolution of the film.
The environment shall benefit, as the disposal of release liners shall be avoided.